Dissipation and Evaluation of Metaldehyde Residues in Cabbage Grown in Open Fields

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The residual levels and dissipation rates of metaldehyde in cabbage and soil at three main cabbage-growing areas in china were determined by A simple，rapid and sensitive analytical method with liquid chromatography with TripleQuad mass spectrometry (LC–MS–MS). The limit of quantification (LOQ) was 0.0005,0.0005mg/kg for soil and cabbage, respectively. The mean half-life of metaldehyde was 5.84 days in cabbage and 3.17 days in soil. The final residues in cabbage and soil detected at 7 days after the last spreading were considerably all below 1mg/kg (the MRL of China). Low residues in cabbage and soil suggest that this pesticide may be safe to use under the recommended dosage.

Abstract: Pot-mode cultivation experiments were carried out to study the impacts of nitrogen（urea）fertilization in different level on Cadmium (Cd) accumulation, nitrate contents and nutritive values in Chinese cabbage, The results showed that: at different level of Cd artificial enriched soil, with applied urea increased, the accumulation of Cd in edible part of Chinese cabbage gradually decreased. Nitrate Contents in edible part have a positive correlation with the concentration of Cd in soil and the nitrogen fertilizer applied. In the natural soil (with contaminated Cd in concentration of 0.18 mg/kg), when the urea was fertilized by 255 kg/hm2 to 330 kg/hm2, Cd and nitrate contents of edible parts of cabbage were within the national food security limits, which could guarantee the food security of Chinese cabbage. Increasing nitrogen fertilization in the form of urea has a certain effect on amino acids contents but little effect on soluble sugar contents in Chinese cabbage, when the concentration of urea was 320 kg/hm2, amino acids contents of cabbage reached the highest level of 355 mg/kg1. Increasing nitrogen fertilization could lower down the contents of water-soluble Cd and the available Cd in soil, thereby reduce the absorption of Cd by Chinese cabbage. To a certain extent, increasing nitrogen fertilization could increase the food security of Chinese cabbage.

Abstract: In order to simplify the pretreatment process in detection of pesticide residues in vegetables and improve the extraction recovery, an ultrahigh pressure technique was adopted in pretreatment experiments on organophosphorus pesticide residues in cabbage, and on the basis of single-factor test, orthogonal pre-conditions were optimized. The results showed that: The optimum process conditions for ultrahigh pressure extraction of dimethoate in cabbage at room temperature are: pressure of 400MPa, extraction solvent volume of 60ml, the holding time of 4min, recovery rate up to 91.3%, compared with the conventional homogenization method, extraction efficiency improved significantly.

Abstract: 33 species Chinese cabbage sold in local market were seeded and growth on Cd polluted (Cd 0.65-9.0 mg/kg) soil in the old irrigation area, Shenyang, P.R.China. The harvested Chinese cabbages were collected for analysis of Cd content, soluble protein and soluble sugar, respectively. Results showed that the Cd content in edible parts of varieties Chinese cabbage does not exceed, partly exceed and all out of the allowed standard of 0.2 mg/kg fresh weight Cd, as the soil Cd contents were in the range of 0.65-1.8 mg/kg, 1.81-4.17 mg/kg and 4.18 to 5.3 mg/kg. Soil Cd content has a positive correlation with Cd content in the edible part of all varieties of Chinese cabbage. And soluble sugar and soluble protein showed increased trend as soil cd increase. According to above results, we concluded that the products of Chinese cabbage is relatively safety in quality if growth in soil with Cd content from 0.65 to 1.81 mg/kg , and appropriate screening of low Cd uptake species for Chinese cabbage is necessary as soil Cd content was from 1.81-4.17 mg/kg, to insure the safety of agricultural products , and suitable remediation technology should be used as soil Cd content was from 4.18-5.3 an till 9.0 mg/kg, in order to reduce the food-chains transportation risk brought by Cd accumulated in Chinese cabbage.